Where would you buy vanilla extract to rub on a dog's nose?
Vanilla extract contains alcohol, and alcohol is not appropriate for application to an area as sensitive as a dog's nose. The result would be intense pain and drying; it is no less than abusive to apply such a substance to a dog's nose, and no veterinarian would approve of it. Also, dogs have extremely acute senses of smell and vanilla extract has a very strong odor to it - this would be the equivalent of putting an air horn to your ear and hitting the button. It would be extremely painful and there's no reason to be that cruel.
Never apply anything to a dog's nose other than clean lukewarm water if and only if the outside of the nose needs cleaning.
Actually most modern vanilla extracts are alcohol free and use polyethylene glycol instead as the solvent. However its still probably not a good idea to put it on anyone's nose.
Where did you happen to get this strange idea from?